Polyetherimide/epoxy chopped fiber reinforced laminates and the preparation thereof

Abstract

The present invention is directed to a method for making a chopped fiber-reinforced composite. The method comprises dispersing a polyamide acid/epoxy blend and greater than 50 wt-% chopped fiber in an aerated surfactant foam. The foam is deposited on a foraminous layer and collapsed to form a web. The web is consolidated at a temperature of greater than about 280° C. and a pressure of greater than about 500 psi. The resulting composite typically has a flexural modulus of greater than 2,000 ksi and flexural strength values of greater than about 30,000 psi and typically between about 30,000 and 50,000 psi. The composite should find use in applications requiring effective high mechanical stiffness and strength, and flame resistance.

I claim: 
     
       1. A method for making a chopped fiber-reinforced composite which comprises: (a) dispersing a polyamide acid/epoxy blend and greater than 50 wt-% chopped fiber in an aerated surfactant foam;   (b) depositing said foam on the foraminous layer and collapsing said foam to form a web; and   (c) consolidating said web at a temperature of greater than 280° C. and a pressure greater than about 500 psi.   
     
     
       2. The method of claim 1 wherein said polyamic acid and said epoxy are a physical blend. 
     
     
       3. The method of claim 1 wherein said polyamide acid and said epoxy are prereacted. 
     
     
       4. The method of claim 1 wherein one or more of said polyamide acid or said epoxy are flame retardant. 
     
     
       5. The method of claim 4 wherein flame retardancy is provided by bromine groups. 
     
     
       6. The method of claim 1 wherein said fiber is one or more of glass, organic, or ceramic. 
     
     
       7. The method of claim 6 wherein said fiber is glass. 
     
     
       8. The method of claim 1 wherein said fiber ranges in length between about 0.125 and 0.75 inches.